This invention relates to compositions of plasticized polyvinyl chloride resins and polyolefins.
A variety of rigid polyvinyl chloride (PVC) resin and polyolefin blends is known. As these two materials are normally incompatible, compatibilizers are sometimes added to improve the physical and mechanical properties of the blends. Blends made from rigid PVC and polyolefins are useful in applications such as the manufacture of rigid plastic pipes and tubing.
Plasticized PVC has different properties than rigid PVC; it is more flexible than non-plasticized PVC and can therefore be used in different applications. Plasticized PVC compositions can be used, for example, as wire and cable insulation and jacketing, in automotive applications, and as components of medical devices.
In a first aspect, the invention features a thermoplastic composition that includes a plasticized polyvinyl chloride resin; a polyolefin, preferably a polyolefin that is a thermoplastic elastomer; and a compatibilizer. The composition preferably contains at least about 5 parts of the polyolefin and at least about 5 parts of the compatibilizer (based on 100 parts by weight of the plasticized polyvinyl chloride resin).
The composition may further include a styrenic polymer, preferably a styrenic polymer that is a thermoplastic elastomer. It is preferred that the combined amount of the polyolefin and the styrenic polymer in this composition is at least about 5 parts (based on 100 parts by weight of the plasticized polyvinyl chloride resin).
In another aspect, the invention features a thermoplastic composition that includes a plasticized polyvinyl chloride resin; a styrenic polymer, preferably a thermoplastic elastomer; and a compatibilizer. The composition preferably contains at least about 5 parts of the styrenic polymer and at least about 5 parts of the compatibilizer (based on 100 parts by weight of the plasticized polyvinyl chloride resin).
The compositions exhibit excellent retention of mechanical properties after being aged. For example, preferred compositions have elongation retentions of about 65% to about 150%. Preferred compositions also have tensile strength retentions of about 65% to about 200%. In addition, the brittle points of preferred compositions increase less than about 5xc2x0 C. after the compositions have been aged.
The term xe2x80x9caged,xe2x80x9d as used herein, means that a composition or material has been subjected to 125xc2x0 C. heat for a period of 7 consecutive days.
Other features and advantages of the invention will be apparent from the following description of the preferred embodiments thereof, and from the claims.
A preferred composition includes a plasticized polyvinyl chloride resin, a polyolefin, and a compatibilizer.
xe2x80x9cPolyvinyl chloridexe2x80x9d or xe2x80x9cPVC,xe2x80x9d as used herein, include homopolymers of vinyl chloride, as well as polymerization products of vinyl chloride and one or more co-monomers. For example, the polyvinyl chloride resin can be a copolymer of vinyl chloride and ethylene, or a copolymer of vinyl chloride and propylene. The polyvinyl chloride resin can also be the polymerization product of vinyl chloride and an ester monomer having the formula H2Cxe2x95x90C(R1)C(xe2x95x90O)OR2, where R1 and R2 are, independently, C1-12 alkyl. An example of such a resin is a copolymer of a vinyl chloride monomer and a methyl methacrylate monomer. These resins may be used alone or in combination.
xe2x80x9cPlasticized polyvinyl chloridexe2x80x9d or xe2x80x9cplasticized PVC,xe2x80x9d as used herein, include PVC plasticized with an internal plasticizer (i.e., a co-monomer that is co-polymerized with vinyl chloride monomer) or an external plasticizer (i.e., a compound that is incorporated into PVC). Preferably, the compositions contain at least about 10 parts plasticizer (based on 100 parts by weight of the polyvinyl chloride resin). Suitable plasticizers include phthalates, trimelletates, pyromelletates, azelates, adipates, polyesters, pentaerythritol esters, ethylene/vinyl acetate copolymers, and butyl/acrylate/carbon monoxide terpolymers. The plasticizers may be used alone or in combination. A preferred plasticizer is dioctyl phthalate.
The compositions preferably contain at least about 5 parts, and more preferably at least about 10 parts, of the polyolefin (based on 100 parts by weight of the plasticized polyvinyl chloride resin). It is preferred that the polyolefin is a thermoplastic elastomer. Suitable polyolefins include homopolymers, such as polyethylene and polypropylene. Suitable polyolefins also include copolymers that are thermoplastic elastomers, such as a copolymer of ethylene and propylene (EP rubber); a copolymer of ethylene and an xcex1-olefin having at least 4 carbons; or a copolymer of ethylene, propylene, and a non-conjugated diene monomer (EPDM). The polyolefins may be used alone or in combination.
The polyolefins can be in various forms. For example, the polyethylene used in the invention can be any form of polyethylene, such as high density polyethylene (HDPE), low density polyethylene, (LDPE), linear low density polyethylene (LLDPE), or very low density polyethylene (VLDPE).
Preferred polyolefins include a copolymer of ethylene and 1-octene that is a metallocene-catalyzed reaction product of these two monomers (with 25% 1-octene), available from DuPont-Dow Elastomers under the trade name ENGAGE 8150; a copolymer of ethylene, propylene, and a non-conjugated diene monomer (EPDM), available from Uniroyal Chemical under the trade name ROYALENE 580HT; and a copolymer of ethylene and 1-butene, available from Exxon Chemicals under the trade name EXACT 3035.
Since plasticized polyvinyl chloride resins and polyolefins are normally incompatible, compositions that include these ingredients generally have poor mechanical properties. The addition of certain compounds (suitably called compatibilizers) enhances the compatibility of the plasticized polyvinyl chloride resin and the polyolefins; the resulting compositions can therefore have desired mechanical properties.
Preferred compositions contain at least about 5 parts, and more preferably at least about 10 parts, of the compatibilizer (based on 100 parts by weight of the plasticized polyvinyl chloride resin). Suitable compatibilizers include chlorinated polyolefins; polyolefin-polyurethane graft copolymers (preferably produced by reactive extrusion of functionalized polyolefins and polyurethanes); hydrogenated styrene-butadiene-styrene-polyester tetrablock copolymers; and hydrogenated styrene-isoprene-styrene-polyester tetrablock copolymers. The compatibilizers may be used alone or in combination.
When chlorinated polyethylene (CPE) is used as the compatibilizer, it is preferred that the CPE has a chlorine content of about 5% to about 50% by weight. It is also preferred that the CPE is the chlorinated product of a slurry process. The chlorination process generally decreases the crystallinity of the material; it is preferred that the CPE has a residual polyethylene crystallinity of at least about 0.5% (measured by differential scanning calorimetry). A preferred compatibilizer is chlorinated polyethylene, available from Dow Chemical under the trade name TYRIN 3623A.
Another preferred composition includes a plasticized polyvinyl chloride resin, a polyolefin, a styrenic polymer, and a compatibilizer. It is preferred that the combined amount of the polyolefin and the styrenic polymer in this composition is at least about 5 parts, and more preferably at least about 10 parts (based on 100 parts by weight of the plasticized polyvinyl chloride resin). It is also preferred that the styrenic polymer is a thermoplastic elastomer. Suitable styrenic polymers include styrene-butadiene-styrene triblock copolymers (SBS), hydrogenated styrene-butadiene-styrene triblock copolymers (SEBS), hydrogenated styrene-butadiene diblock copolymers (SEB), styrene-isoprene-styrene triblock copolymers (SIS), hydrogenated styrene-isoprene-styrene triblock copolymers (SEPS), and hydrogenated styrene-isoprene diblock copolymers (SEP). The styrenic polymers may be used alone or in combination. A preferred styrenic polymer is a hydrogenated styrene-butadiene-styrene triblock copolymer, available from Shell Chemical under the trade name KRATON G-1652.
Another preferred composition includes a plasticized polyvinyl chloride resin, a styrenic polymer, and a compatibilizer. The composition preferably contains at least about 5 parts, and more preferably at least about 10 parts, of the styrenic polymer (based on 100 parts by weight of the plasticized polyvinyl chloride resin). Suitable amounts of each of the other components, as well as suitable examples of each of these components, are as described above.
The preferred compositions may also contain ingredients such as lubricants, stabilizers, antioxidants, and fillers.. Examples of suitable lubricants include stearic acid, metal salts of stearic acid, wax, and polyethylene glycols. The lubricants may be used alone or in combination. Preferred lubricants include stearic acid, available from Henkel Corporation as Stearic Acid GP Grade, and zinc stearate, available from The Norac Company under the trade name COAD 21.
Examples of suitable stabilizers include barium/zinc heat stabilizers, lead stabilizers, and organic heat stabilizers. The stabilizers may be used alone or in combination. Preferred stabilizers include a barium/zinc stabilizer, available from Witco under the trade name MARK 4782-A, and epoxidized soybean oil, available from Witco under the trade name E-54 EPO.
Examples of suitable antioxidants include phenolic and thioester antioxidants. The antioxidants may be used alone or in combination. A preferred antioxidant is tetrakis[(methylene (3,5-di-t-butyl-4-hydroxylhydrocinnamate)]methane, available from Ciba Geigy under the trade name IRGANOX 1010.
Examples of suitable fillers include Kaolin clay, calcium carbonate, and other fillers commonly used in PVC compositions. The fillers may be used alone or in combination.
The compositions are generally prepared according to conventional dry blend or wet blend methods known to those skilled in the art of PVC compounding.
The mixtures obtained from the blending process can be further compounded with a mixer such as a BANBURY(copyright) batch mixer, a Farrel Continuous Mixer, or a single or twin screw extruder.
The compositions are useful in a variety of applications. For example, these compositions are useful in applications in which it is desirable for compositions to maintain mechanical properties such as tensile strength, elongation, and a low brittle point, even when the compositions are subjected to high temperatures for extended periods of time. Such applications include wire and cable insulation and jacketing, garden hoses, medical devices, automotive parts, and construction materials.